An example of a soft medical device includes a soft contact lens which is a commercially available soft lens for eye. A hydrogel material having a water content of about 25 to 80% is commonly used in the commercially available soft contact lens. However, since the low water content soft contact lens made of the hydrogel material contains water, there arises a phenomenon in which water is vaporized from the contact lens. Thereby, a certain proportions of contact lens wearers felt dry more strongly as compared with the case of the naked eye, and thus felt uncomfortable. Among these contact lens wearers, some persons complained a condition of so-called contact lens-related dry eye. Since a water-containing soft contact lens made of a hydrogel material is likely to be contaminated with components in a lacrimal fluid and also contains a large amount of water, there was also a risk of the growth of bacteria.
There has been known, as a highly oxygen permeable low water content soft contact lens, for example, a silicone rubber lens obtained by a method of adding a platinum-based catalyst to a mixture of polydimethylsiloxane in which both ends of the molecular chain are blocked with a vinylmethylsilyl group, and methyl hydrogen polysiloxane, followed by heat-curing using a molding method (see, for example, Patent Literature 1).
Patent Literatures 2 to 7 also disclose a highly oxygen permeable contact lens material composed mainly of polysiloxane having a plurality of polymerizable functional groups. Of these, Patent Literature 6 discloses a contact lens material made of a polymer obtained by polymerizing a difunctional organosiloxane macromer alone, or a polymer obtained by copolymerizing a difunctional organosiloxane macromer with the other monomers, and also discloses an acrylic acid fluoroalkyl ester or a methacrylic acid fluoroalkyl ester, and an acrylic acid alkyl ester or a methacrylic acid alkyl ester as a monomer to be used in copolymerization.
Meanwhile, the following problems also lie in a conventional highly oxygen permeable low water content soft contact lens. A silicone rubber lens has such a drawback that a hydrophilized layer formed so as to improve hydrophobicity of the surface of the lens is peeled, or adhesion of the lens to the cornea occurs due to too large resilience, and thus the silicone rubber lens had not widely been put into practice.
A material composed mainly of polysiloxane having a plurality of polymerizable functional groups has high oxygen permeability and also has flexibility, and the material is considered to be one of materials which are suitable for a contact lens. However, since tackiness is left on the surface of the lens after polymerization, the lens may adhere to the cornea and is also insufficient in balance between flexibility of the lens and mechanical properties such as folding resistance.
There have been known various methods for modification of a surface of a soft lens for eye. Among these methods, there is known a method in which layers of two or more kinds of polymer materials are coated and accumulated in a layer by layer fashion (see, for example, Patent Literatures 8 to 10). Among these methods, a method of alternately forming layers made of two polymer materials, each having an opposite electric charge, in a layer by layer fashion by coating is called an LbL method, and it is considered that each layer of the material is noncovalently bonded to the other layer made of a different material.
However, the highly oxygen permeable soft lens for eye in which utility of the method disclosed in Patent Literature 1 is clearly shown is made only of a silicone hydrogel material, and utility to the low water content soft lens for eye has not been known. Conventional LbL coating was carried out to obtain a multi-layered structure constituted from about 4 to 20 layers, and thus the production process may increase, to cause an increase in production costs.
In the above-mentioned soft contact lens, there has been known a contact lens in which the color or size of iris portions of lens wearers can be changed by forming an iris pattern, which is an iris-like and approximately cyclic mask, to the lens (see, for example, Patent Literatures 11 and 12). There has also been known a contact lens in which formation of a hole (pinhole) at approximately center of the iris pattern enables clear vision irrespective of hyperopia, myopia, and presbyopia (see, for example, Patent Literatures 13 and 14). However, the same problems as those mentioned above arose when the iris pattern is formed to the contact lens (low water content soft device for eye) produced by the above-mentioned method.
In the above-mentioned soft contact lens, there has also been known a contact lens in which formation of a lacrimal fluid exchange-promoting pattern on the contact lens enables exchange of a lacrimal fluid during wearing of lenses (see, for example, Patent Literatures 15 to 18). However, the same problems as those mentioned above arose when the lacrimal fluid exchange-promoting pattern is formed to the contact lens produced by the above-mentioned method.